1. Field of the Invention
The present invention relates to an image heating apparatus heating a toner image on a recording material, and more particularly to an image heating apparatus provided with a rubbing rotating body which rubs a heating rotating body heating the toner image on the recording material. The image heating apparatus is used in an image forming apparatus such as a copier, a printer, a facsimile machine, and a complex machine having the functions thereof.
2. Description of the Related Art
Conventionally, in an image forming apparatus utilizing an electrophotographic system or the like, a toner image formed on a recording material is pressurized and heated at a nip portion between a heating rotating body and a nip forming member. A material, such as fluororesin, having an excellent releasing property, is used for a surface of the heating rotating body.
Among recording materials, there is a recording material having a protrusion called an “edge protrusion”, which is formed at an edge of the recording material. When the recording material passes through a nip, a fine scuff may be formed on a heating rotating body by the edge of the recording material. Since portions through which the edge of the recording material passes are concentrated in a width direction perpendicular to a direction of conveying the recording material, the fine scuffs due to the edge protrusion may be locally formed. Consequently, streaks b (see, FIG. 5) are formed on an image.
As measures against the scuffs due to the edge protrusion, Japanese Patent Application Laid-Open No. 2008-40363 discloses a method of rubbing the heating rotating body with rubbing member. The rubbing member uniformly rubs the heating rotating body, and therefore the fine scuffs concentrated in two portions in a conveyance width direction of the heating rotating body become unnoticeable. In order to prevent a surface of the rubbing member from being contaminated, the rubbing member is usually spaced apart from a heating member, and, in order to rub the surface of the heating rotating body every time a predetermined number of images are formed, the operation of bringing the rubbing member into abutment against the heating rotating body is performed.
However, the viscosity of fluororesin tends to decrease as the temperature increases (FIG. 7). Thus, the depth of a recess of a heating rotating body formed by the rubbing member depends on the surface temperature of the heating rotating body. When the rubbing member rubs the heating rotating body when a temperature difference between a central portion and an end portion in the width direction of the heating rotating body is large, the rubbing by the rubbing member may become nonuniform due to the difference of the viscosity of the fluororesin of the surface of the heating rotating body.